1. Field of the Invention
The invention relates to audio processing systems and particularly audio processing systems that enhance audio communications in sound-dominated environments.
Personal audio players are nearly ubiquitous. The popularization of smartphones has ushered in an environment where anyone and everyone with a smartphone has an on-board personal audio player. Personal audio is typically delivered to a user by headphones. Headphones are a pair of small speakers that are designed to be held in place close to a user's ears. They may be electroacoustic transducers which convert an electrical signal to a corresponding sound in the user's ear. Headphones are designed to allow a single user to listen to an audio source privately, in contrast to a loudspeaker which emits sound into the open air, allowing anyone nearby to listen. Earbuds or earphones are in-ear versions of headphones.
2. Description of the Related Technology
Active noise reduction; active noise cancellation and active noise control are known in the prior art, Elliot, S. J. et al., “Active Noise Control,” IEEE Signal Processing Magazine, October 1993 (pages 12-35), the disclosure of which is expressly incorporated by reference herein, describes the history and background of active noise control systems and describes the use of adaptive filters.
Kuo, Sen M. et al., “Active Noise Control: A Tutorial Review,” Proceeding of the IEEE, Vol. 87, No. 6, June 1999 (pages 943-973), the disclosure of which is expressly incorporated by reference herein, describes principles and systems for active noise control.
Kuo, Sen M. et al., “Design of Active Noise Control Systems with the TMS320 Family,” Application Report, Texas Instruments Digital Signal Processing Solutions, Digital Signal Processing Products—Semiconductor Group, SPRA042, June 1996, the disclosure of which is expressly incorporated by reference herein, describes specialized digital signal processors designed for real-time processing of digitized signals and details the design of an Active Noise Control (“ANC”) system using a TMS320 DSP.
United States Published Patent Application US 2014-0044275, the disclosure of which is expressly incorporated by reference herein, describes an active noise control system with compensation for error sensing at the ear drum including a subjective tuning module and user control.
Active noise control systems utilize various active filtration techniques and rely on algorithms to process source audio in order to reduce the influence of noise on the listener. This may be accompanied by modification of the source audio by combination with an “anti-noise” signal derived from comparing ambient sound to source audio at the ear of a listener.
Active noise control devices in the prior art suffer from being incapable of addressing the wide variation of ambient sound and dominant noise. The particular acoustic sensors used and specific characteristics of headphones or earphones or other listening devices add another layer of complexity to any active noise control system. Furthermore, the type, nature and characteristics of source audio (such as sound from a digital electronic device) are variables ignored in active noise control devices. Finally, individual audio perceptions of each of these and other elements of sound interact to comprise a listening experience are not adequately addressed by active noise control systems.
Adaptive noise cancellation is described in Singh, Arti. “Adaptive Noise Cancellation,” Dept. of Electronics & Communications, Netaji Subhas Institute of Technology, (2001). http://www.cs.cmu.edu/naarti/pubs/ANC.pdf#. Accessed Nov. 21, 2014, the disclosure of which is incorporated herein. The customization according to the invention may be performed in accordance with the principles described therein.
Advancements in hearing aid technology have resulted in numerous developments which have served to improve the listening experience for people with hearing impairments, but these developments have been fundamentally limited by an overriding need to minimize size and maximize invisibility of the device. Resulting limitations from miniaturized form factors include limits on battery size and life, power consumption and, thus, processing power, typically two or fewer microphones per side (left and right) and a singular focus on speech recognition and speech enhancement.
Hearing aid technology may use “beamforming” and other methods to allow for directional sound targeting to isolate and amplify just speech, wherever that speech might be located.
Hearing aid technology includes methods and apparatus to isolate and amplify speech and only speech, in a wide variety of environments, focusing on the challenge of “speech in noise” or the “cocktail party” effect (the use of directional sound targeting in combination with noise cancellation has been the primary approach to this problem).
Hearing aid applications typically ignore or minimize any sound in the ambient environment other than speech. Hearing devices may also feature artificial creation of sounds as masking to compensate for tinnitus or other unpleasant remnants of the assistive listening experience for those suffering from hearing loss.
Due to miniature form factors, hearing aids are constrained by a severe restriction on available power to preserve battery life which results in limitations in signal processing power. Applications and devices not constrained by such limitations may provide a high quality listening experience. Such applications and devices are able to utilize high quality signal processing, which among other things, may maintain a high sampling rate, typically at least twice that of the highest frequency that can be perceived. Music CDs have a 44.1 kHz sampling rate to preserve the ability to process sound with frequencies up to about 20 kHz. Most hearing aid devices sample at rates significantly below 44.1 kHz, resulting in a much lower range of frequencies that can be analyzed for speech patterns and then amplified, further necessitating the use of compression and other compensating methodologies in an effort to preserve the critical elements of speech recognition and speech triggers that reside in higher frequencies.
Hearing aids may require compensation for hearing loss at high frequencies, and may require greater levels of amplification in higher and lower frequencies than in midrange frequencies. One strategy to achieve this has been compression (wide dynamic range compression or WDRC) whereby either the higher frequency ranges are compressed to fit within a lower frequency band, or less beneficially, higher frequency ranges are literally cut and pasted into a lower band.
For these reasons hearing aid technologies do not adequately function within the higher frequency bands where a great deal of desired ambient sound exists for listeners, and hearing aids and their associated technologies have neither been developed to, nor are capable as developed, to enhance the listening experience for listeners who do not suffer from hearing loss but rather want an optimized listening experience.
Neither hearing aid nor active noise cancellation technologies are capable of permitting users to communicate with others in their presence while also permitting admission of desirable audio information to the user.